As electronic components become larger, faster, and more powerful, they also generate more heat. Effective cooling of heat-generating, devices, such as microprocessors used in pocket computers, laptops, and other devices, is becoming an increasingly important consideration. With processor speeds exceeding several GHz, and with multiple CPUs and memory units fabricated on a single chip producing high component densities, cooling semiconductor devices is critical to product reliability.
The relatively low power operation of many older processors allowed the use of traditional air-cooled heat sinks for heat control. These traditional methods use heat sinks coupled to a single device or to a number of devices within a chassis to conduct heat away from the device or devices. The heat sinks may optionally be cooled by fans. Air cooled heat sinks typically provide only limited capacity for heat removal and provide little capacity for moderating thermal gradients within a chassis or over the surface of a single device.
Higher power components require substantially greater heat dissipation than air-cooled heat sinks can provide and require more effective cooling methods. One such method denoted spray cooling, involves the application of a liquid coolant onto the surface of the component. Current sprayer designs commonly employ either pressurized liquid spraying (i.e., pressure-assisted spraying) or pressurized gas atomizing.
Spray cooling configurations typically spray a uniform or uncontrollably varied distribution of coolant across each chip. Spray cooling systems arc difficult to control and are limited in their ability to limit “pooling” of the fluid (i.e., building up of liquid on the cooled device due to excessive spray rates). In addition, high power semiconductor components, such as microprocessors, may incorporate some areas, e.g., the CPU, that generate significantly more heat than other areas of the component. Thus, thermal gradients across a heat generating component may result in insufficient cooling resources directed to some areas of the component by spray cooling systems.